Just looked at that fake url address in the first post
I found this post which explains things.
"This appears to be webkit's way of pasting local images into rich editors. For example, open an image from your computer in OS X's Preview application. Select all, copy, and paste into the rich editor in XF (using Safari or some other webkit browser).
Clearly this is user fail. You obviously cannot paste a local image into a forum post without uploading it as an attachment, or uploading it to some other online location. Webkit just has a strange way of handling this which allows the user to submit the post thinking that it will work. The fix is to educate your users."
Bit brutally phrased but you cannot paste images directly into a post and have it show upon the net. Webkit seems to have an odd way of doing things, its very confusing.
When you think about it anything accessable on the internet has to be publically accessable and most peoples computers are not accessable from the internet, the NSA might disagree but not publically...
There is no standardised universal method for uploading images to the web so each website will be different.